Method and apparatus for transmitting and receiving signal for device-to-device terminal in wireless communication system

ABSTRACT

Disclosed is a method for transmission of a device-to-device (D2D) signal by a terminal in a wireless communication system. The method for transmission of a D2D signal, according to an embodiment of the present invention, comprises the steps of: receiving a location of resources, for transmitting a scheduling assignment, from a base station; and transmitting the scheduling assignment by means of the resources, wherein the scheduling assignment comprises information indicating a subframe, for transmitting a D2D-related signal in a scheduling assignment period that is subsequent to the subframe in which the scheduling assignment is transmitted.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2014/010191, filed on Oct. 28, 2014,which claims the benefit of U.S. Provisional Application Nos.61/896,652, filed on Oct. 28, 2013, 61/952,853, filed on Mar. 13, 2014,61/971,519, filed on Mar. 27, 2014, 61/977,073, filed on Apr. 8, 2014,61/989,505, filed on May 6, 2014, 61/990,096, filed on May 7, 2014,61/992,212, filed on May 12, 2014 and 62/001,619, filed on May 21, 2014,the contents of which are all hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

Following description relates to a wireless communication, and moreparticularly, to a method of transmitting and receiving device-to-device(D2D) signal in device-to-device communication and an apparatustherefor.

BACKGROUND ART

Wireless communication systems are widely deployed to provide variouskinds of communication content such as voice and data. Generally, thesecommunication systems are multiple access systems capable of supportingcommunication with multiple users by sharing available system resources(e.g., bandwidth and transmit power). Examples of multiple accesssystems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency-division multipleaccess (SC-FDMA) system, and a multi-carrier frequency division multipleaccess (MC-FDMA) system.

A device-to-device (hereinafter abbreviated D2D) communicationcorresponds to a communication scheme transmitting and receiving audio,data and the like between UEs without passing through an evolved Node B(hereinafter abbreviated eNB) by configuring a direct link between theUEs. The D2D communication can include such a communication scheme as aUE-to-UE communication scheme, a peer-to-peer communication scheme andthe like. The D2D communication scheme can be applied to a M2M(machine-to-machine) communication, MTC (machine type communication) andthe like.

The D2D communication is considered as a method of solving a burden ofan eNB resulted from increasing data traffic. For instance, unlike alegacy wireless communication system, the D2D communication transmitsand receives data between devices without passing through an eNB. Hence,the D2D communication can reduce network overload. Moreover, if the D2Dcommunication is introduced, it may be able to expect reduced proceduresof an eNB, reduced power consumption of devices participating in theD2D, increased data transmission speed, increased network capacity, loaddistribution, and enlarged a cell coverage and the like.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina transmitting/receiving method related to control information and ascheduling assignment signal in device-to-device (D2D) communication.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

In an aspect of the present invention, provided herein is a method oftransmitting a device-to-device (D2D) signal by a user equipment (UE) ina wireless communication system, the method including receiving locationinformation of resources for transmission of a scheduling assignmentfrom a base station, and transmitting the scheduling assignment throughthe resources.

The scheduling assignment includes information indicating a subframetransmitting a D2D-related signal in a scheduling assignment periodconsecutive to a subframe in which the scheduling assignment istransmitted.

In another aspect of the present invention, provided herein is a methodof transmitting a device-to-device (D2D) signal by a UE in a wirelesscommunication system, the method including selecting resources fortransmission of a scheduling assignment from a resource pool for thescheduling assignment, and transmitting the scheduling assignmentthrough the resources. The scheduling assignment includes informationindicating a subframe transmitting a D2D-related signal in a schedulingassignment period consecutive to a subframe in which the schedulingassignment is transmitted.

The above aspects of the present invention may include some or all ofthe following description.

The scheduling assignment may include a modulation and coding scheme(MCS) to be used in the scheduling assignment period.

The MCS may indicate only some of modulation techniques to be used whenthe UE transmits/receives a signal to/from the base station.

The some modulation techniques may not comprise 64 quadrature amplitudemodulation (QAM).

The scheduling assignment may include identification (ID) information.

The ID information may be related to the UE using the schedulingassignment.

Advantageous Effects

According to the present invention, control information and a schedulingassignment signal may be efficiently transmitted/received in D2Dcommunication.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram for a structure of a radio frame.

FIG. 2 is a diagram for a resource grid in downlink slot.

FIG. 3 is a diagram for a structure of a downlink subframe.

FIG. 4 is a diagram for a structure of an uplink subframe.

FIGS. 5 and 6 are diagrams illustrating information included in controlinformation.

FIGS. 7 to 9 are diagrams illustrating resource patterns fortransmission.

FIGS. 10 and 11 are diagrams illustrating the structures of a controlchannel.

FIG. 12 is diagram illustrating resource patterns for piggybacking of aHybrid automatic repeat request ACKnowledgment (HARQ-ACK) and an rankindicator (RI).

FIG. 13 is a block diagram of a transmitting/receiving apparatus.

BEST MODE

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions or features ofany one embodiment may be included in another embodiment and may bereplaced with corresponding constructions or features of anotherembodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between aBase Station (BS) and a User Equipment (UE). The BS is a terminal nodeof a network, which communicates directly with a UE. In some cases, aspecific operation described as performed by the BS may be performed byan upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘relay’ may be replaced with the term ‘Relay Node(RN)’ or ‘Relay Station (RS)’. The term ‘terminal’ may be replaced withthe term ‘UE’, ‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’,‘Subscriber Station (SS)’, etc. In the following description, the term‘base station’ may be used to indicate a device such as a schedulingperforming node, a cluster header, or the like. If a base station or arelay transmits such a signal that a UE transmits, it may also beconsidered as a type of terminal.

Cells to be described below may represent transmission/reception pointssuch as a base station (eNB), a sector, a remote radio head (RRH), arelay, etc., and may be used as comprehensive terms for identifyingcomponent carriers at a specific transmission/reception point.

Specific terms used for the embodiments of the present invention areprovided to help the understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3rdGeneration Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA 2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunications System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN)-OFDMA Reference System) and theIEEE 802.16m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE and LTE-A systems. However, thetechnical features of the present invention are not limited thereto.

LTE/LTE-A Resource Structure/Channel

With reference to FIG. 1, the structure of a radio frame will bedescribed below.

In a cellular Orthogonal Frequency Division Multiplexing (OFDM) wirelesspacket communication system, uplink and/or downlink data packets aretransmitted in subframes. One subframe is defined as a predeterminedtime period including a plurality of OFDM symbols. The 3GPP LTE standardsupports a type-1 radio frame structure applicable to Frequency DivisionDuplex (FDD) and a type-2 radio frame structure applicable to TimeDivision Duplex (TDD).

FIG. 1(a) illustrates the type-1 radio frame structure. A downlink radioframe is divided into 10 subframes. Each subframe is further dividedinto two slots in the time domain. A unit time during which one subframeis transmitted is defined as a Transmission Time Interval (TTI). Forexample, one subframe may be 1 ms in duration and one slot may be 0.5 msin duration. A slot includes a plurality of OFDM symbols in the timedomain and a plurality of Resource Blocks (RBs) in the frequency domain.Because the 3GPP LTE system adopts OFDMA for downlink, an OFDM symbolrepresents one symbol period. An OFDM symbol may be referred to as anSC-FDMA symbol or symbol period. An RB is a resource allocation unitincluding a plurality of contiguous subcarriers in a slot.

The number of OFDM symbols in one slot may vary depending on a CyclicPrefix (CP) configuration. There are two types of CPs: extended CP andnormal CP. In the case of the normal CP, one slot includes 7 OFDMsymbols. In the case of the extended CP, the length of one OFDM symbolis increased and thus the number of OFDM symbols in a slot is smallerthan in the case of the normal CP. Thus when the extended CP is used,for example, 6 OFDM symbols may be included in one slot. If channelstate gets poor, for example, during fast movement of a UE, the extendedCP may be used to further decrease Inter-Symbol Interference (ISI).

In the case of the normal CP, one subframe includes 14 OFDM symbolsbecause one slot includes 7 OFDM symbols. The first two or three OFDMsymbols of each subframe may be allocated to a Physical Downlink ControlCHannel (PDCCH) and the other OFDM symbols may be allocated to aPhysical Downlink Shared Channel (PDSCH).

FIG. 1(b) illustrates the type-2 radio frame structure. A type-2 radioframe includes two half frames, each having 5 subframes, a DownlinkPilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot TimeSlot (UpPTS). Each subframe is divided into two slots. The DwPTS is usedfor initial cell search, synchronization, or channel estimation at a UE.The UpPTS is used for channel estimation and acquisition of uplinktransmission synchronization to a UE at an eNB. The GP is a periodbetween an uplink and a downlink, which eliminates uplink interferencecaused by multipath delay of a downlink signal. One subframe includestwo slots irrespective of the type of radio frame.

The above-described radio frame structures are purely exemplary and thusit is to be noted that the number of subframes in a radio frame, thenumber of slots in a subframe, or the number of symbols in a slot mayvary.

FIG. 2 illustrates the structure of a downlink resource grid for theduration of one downlink slot. A downlink slot includes 7 OFDM symbolsin the time domain and an RB includes 12 subcarriers in the frequencydomain, which does not limit the scope and spirit of the presentinvention. For example, a downlink slot may include 7 OFDM symbols inthe case of the normal CP, whereas a downlink slot may include 6 OFDMsymbols in the case of the extended CP. Each element of the resourcegrid is referred to as a Resource Element (RE). An RB includes 12×7 REs.The number of RBs in a downlink slot, NDL depends on a downlinktransmission bandwidth. An uplink slot may have the same structure as adownlink slot.

FIG. 3 illustrates the structure of a downlink subframe. Up to threeOFDM symbols at the start of the first slot in a downlink subframe areused for a control region to which control channels are allocated andthe other OFDM symbols of the downlink subframe are used for a dataregion to which a PDSCH is allocated. Downlink control channels used inthe 3GPP LTE system include a Physical Control Format Indicator CHannel(PCFICH), a Physical Downlink Control CHannel (PDCCH), and a PhysicalHybrid automatic repeat request (HARQ) Indicator CHannel (PHICH). ThePCFICH is located in the first OFDM symbol of a subframe, carryinginformation about the number of OFDM symbols used for transmission ofcontrol channels in the subframe. The PHICH delivers an HARQACKnowledgment/Negative ACKnowledgment (ACK/NACK) signal in response toan uplink transmission. Control information carried on the PDCCH iscalled Downlink Control Information (DCI). The DCI transports uplink ordownlink scheduling information, or uplink transmission power controlcommands for UE groups. The PDCCH delivers information about resourceallocation and a transport format for a Downlink Shared CHannel(DL-SCH), resource allocation information about an Uplink Shared CHannel(UL-SCH), paging information of a Paging CHannel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a Random Access Responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, transmission power controlinformation, Voice Over Internet Protocol (VoIP) activation information,etc. A plurality of PDCCHs may be transmitted in the control region. AUE may monitor a plurality of PDCCHs. A PDCCH is formed by aggregatingone or more consecutive Control Channel Elements (CCEs). A CCE is alogical allocation unit used to provide a PDCCH at a coding rate basedon the state of a radio channel. A CCE includes a plurality of REgroups. The number of CCEs necessary for the PDCCH may be changeddepending on a size, a coding rate and the like of the DCI. Forinstance, one of 1, 2, 4 and 8 CCEs (corresponding to PDCCH formats 0,1, 2, and 3, respectively) can be used for PDCCH transmission. If a DCIsize is large and/or if a low coding rate is required due to a poorchannel state, a relatively large number of CCEs may be used to transmita single PDCCH. An eNB determines a PDCCH format in consideration of asize of DCI transmitted to a UE, a cell bandwidth, the number ofdownlink antenna ports, the amount of PHICH resources, etc. and adds CRC(cyclic redundancy check) to control information. The CRC is masked byan Identifier (ID) known as a Radio Network Temporary Identifier (RNTI)according to the owner or usage of the PDCCH. If the PDCCH is directedto a specific UE, its CRC may be masked by a cell-RNTI (C-RNTI) of theUE. If the PDCCH is for a paging message, the CRC of the PDCCH may bemasked by a Paging Indicator Identifier (P-RNTI). If the PDCCH carriessystem information, particularly, a System Information Block (SIB), itsCRC may be masked by a system information ID and a System InformationRNTI (SI-RNTI). To indicate that the PDCCH carries a Random AccessResponse in response to a Random Access Preamble transmitted by a UE,its CRC may be masked by a Random Access-RNTI (RA-RNTI).

FIG. 4 illustrates the structure of an uplink subframe. An uplinksubframe may be divided into a control region and a data region in thefrequency domain. A Physical Uplink Control CHannel (PUCCH) carryinguplink control information is allocated to the control region and aPhysical Uplink Shared Channel (PUSCH) carrying user data is allocatedto the data region. To maintain the property of a single carrier, a UEdoes not transmit a PUSCH and a PUCCH simultaneously. A PUCCH for a UEis allocated to an RB pair in a subframe. The RBs of the RB pair occupydifferent subcarriers in two slots. Thus it is said that the RB pairallocated to the PUCCH is frequency-hopped over a slot boundary.

Hereinafter, control information (CI) for D2D communication, a method oftransmitting the CI and/or a channel structure for the CI will bedescribed based on the above description and the legacy LTE/LTE-Asystem.

Contents Included in CI or SA

CI may include at least one of information items to be described below.Information items included in the CI, which will be described below, maybe transmitted according to a method to be described with respect to achannel structure for the CI to be described below or may beperiodically transmitted via a separate channel (e.g., a channel for D2Dscheduling assignment). The channel for D2D scheduling assignment may bereferred to as a D2D scheduling assignment channel (D2DSACH). TheD2DSACH may be transmitted in a separate format in a resource regionhaving a predetermined period or may be transmitted in a predeterminedsubframe on determined a frequency domain by a UE before data istransmitted. This D2DSACH may have an existing PUCCH/PUSCH structure ormay have a different format rather than the existing PUSCH/PUCCHstructure. For example, the D2DSACH may be transmitted in a modifiedPUSCH structure which is the same as the PUSCH structure except thatsome last symbols are used as a guard region for timing or Tx/Rxswitching and are thus not transmitted in a subframe. The D2DSACH mayemploy a format such as a D2D discovery format. For example, when a D2Ddiscovery signal is transmitted in the PUSCH structure, the D2DSACH mayalso be transmitted in the PUSCH structure. Here, the “D2D discoverysignal” refers to a signal that a UE transmits to detect the presence ofanother UE or to inform neighboring UEs of the presence of the UEitself. When some or all of CI to be described below is transmitted inthe D2DSACH, some of the remaining D2D CI except for the transmitted CImay be multiplexed and transmitted together with a D2D data packet. Amultiplexing scheme may be one of schemes which will be described below.A new data indicator (NDI) and/or a redundancy version (RV) may betransmitted in a PUSCH piggybacking scheme or NDI information may beindicated using demodulation reference signal cycle shift (DMRS CS). Forexample, it may be determined that a specific value or a specific setvalue is used for DMRS CS when new data is transmitted and anotherspecific value or another specific set value is used for DMRS CS whenretransmission data is transmitted.

Information items to be described below may be transmitted in ascheduling assignment (SA) channel (The D2DSACH described above will bebriefly referred to as an “SA”. More specially, the D2DSACH indicates aformat of a channel transmitting the SA, and the SA indicates a channelitself transmitting some or all of the D2D CI.). For example, when a UEwhich receives location information of resources for transmission of anSA from a base station transmits the SA through the resources, the SAmay include information items to be described below. Alternatively, whena UE selects resources for transmission of the SA from a resource poolfor the SA and transmits the SA through the resources, the SA mayinclude information items to be described below.

a. Resource Allocation Information

Resource allocation (RA) information may be information regardingallocation of time and/or frequency resources for transmission/receptionof a D2D-related signal (e.g., a D2D communication packet) in ascheduling assignment period after the SA is transmitted. The locationof a resource through which the D2D data will (or may) be transmittedmay be indicated by only time, and the location of a frequency thereofmay be implicitly indicated in connection with a location at which CI orSA is transmitted. Alternatively, the locations of the time andfrequency resources may be explicitly indicated. For example, in thecase of the locations of frequency resources, the location of afrequency resource which is transmitted first may be explicitlyindicated, and location information of a subsequent frequency resourcemay be transmitted according to a predetermined frequency hoppingpattern. Location information of the time resource may be transmitted byincluding, in the SA, a bit sequence explicitly indicating the locationof a resource for transmission of a D2D signal.

The RA information may be resource patterns for transmission (RRT) of aD2D signal. In the following description, the RRT may be understood as aT-RPT among RRTs. If the T-RPT is used, a frequency resource region mayhave a specific hopping pattern in a subframe indicated by the T-RPTafter being indicated during first transmission. That is, the RAinformation may be bits indicating a resource transmission pattern. TheRA information may be padded to a specific state (e.g., with all zeros)or may not be included when the length of an ID is long or the number ofRPTs needed is small (e.g., when the number of D2D subframes is apredetermined threshold or less, when the number of times oftransmission is a predetermined threshold or less, or when the RPT maybe sufficiently indicated with only an ID). The RPT will be described inmore detail below.

The RA information may be transmitted in an additional control channelseparated from data to indicate RA information of a data channel. Forexample, as illustrated in FIG. 5, since D2D control channels similar toa PUCCH (which will be hereinafter referred to as a “D2DCCH”) arelocated at both ends of a frequency band (or at a location of a specificsubframe or RB which is determined or configured beforehand) and theD2DCCH includes an RA field of a specific UE, the RA information mayindicate a frequency resource region, for transmitting D2D data,consecutive to a subsequent slot (or subframe) or a predetermined slot(or subframe), e.g., a+n subframe (or slot) (here, ‘n’ may be determinedbeforehand or may be set by a node which manages scheduling between eNBsor between D2D UEs).

Alternately, D2D CI may be multiplexed in a specific region of a datachannel. Thus, a D2D reception UE may obtain the RA information byblind-decoding a D2D CI transmission region. Alternatively, the RAinformation may be obtained by performing energy detection to detect theD2D CI transmission region. For example, as illustrated in FIG. 6, a D2Ddata transmission unit may be sub-channeled into consecutive specific RBunits. Information regarding a D2D sub-channel may be periodicallytransmitted in a D2D synchronization channel, a D2D system informationchannel, or a D2D broadcast channel. Thus, a D2D reception UE whichdecodes the information regarding the D2D sub-channel may know theinformation regarding the D2D sub-channel before the D2D data isreceived. When a symbol for transmission of D2D CI and a symbol fortransmission of data are different from each other, a frequency band fortransmission of the D2D CI may be different from a frequency band of thedata. For example, a frequency band of the D2D CI may always be limitedto 6 RBs or less. Otherwise, the D2D CI may be mapped to a specificsymbol, similar to a PDCCH, and all REs corresponding to a whole systembandwidth may be used for mapping of the D2D CI. Otherwise, a bandwidthfor transmission of the D2D CI may be configured beforehand by a D2Dsynchronization node or a cluster head. In this case, a predeterminedset of symbols near a DMRS may be used to transmit the D2D CI. In theD2D CI, a set of consecutive REs in a frequency domain may be mapped toCI of one D2D link similar to the PDCCH. In this case, when an RE of oneUE corresponds to more than one symbol, the D2D CI may be configured byconsecutively selecting an RE in a subsequent symbol. UEs which receivesuch a D2D CI format may each blind-decode the symbol for transmissionof the D2D CI to detect regions of other symbols to which D2D data isallocated.

b. MCS (Modulation and Coding Scheme)

After the SA is transmitted, an MCS to be used to transmit or receive aD2D-related signal (e.g., a D2D communication packet, etc.) in ascheduling assignment period may be included in the CI or the SA.Alternatively, the MCS may be information indicating an MCS of datawhich is currently transmitted. In this case, a D2D public safetyservice or a specific broadcast service may be limited to use only aspecific MCS (a low MCS index, e.g., MCS 0) or only some MCSs (which aremodulation techniques used when a UE exchanges a signal with a basestation, e.g., MCS indexes 0 to 9 using only QPSK modulation), so that aplurality of UEs may receive the D2D public safety service or thespecific broadcast service. Otherwise, 64QAM may not be used and mayremain in a ‘reserved state’ during transmission of a D2D signal. Inthis case, for D2D, a MCS indication bit length which is shorter thanthat used in the existing PUSCH may be used. Otherwise, the existing MCSindication bit number may be directly used, and unused MCS bits may beused to indicate the D2D CI or may remain in the ‘reserved state’without being used for any purpose.

c. ID Information

Identification (ID) information of a transmission UE (group) and/or areception UE (group) may be explicitly included in the CI or the SA.That is, since ID information related to a UE using the CI or the SA isincluded in the CI or the SA, a UE may determine whether the CI or theSA is available to the UE itself, thereby reducing unnecessary decoding.In other words, when a specific UE receiving a D2D signal determinesthat data is not transmitted from a desired UE, the UE may not decode asubsequent data packet, thereby conserving battery power. Such a D2D IDmay include a packet ID (an application or group ID). Different packetsmay be transmitted from the same UE when one UE transmits a plurality ofdifferent packets, when one UE belonging to a plurality of groupstransmits different data items per group, or when one UE generates andtransmits D2D packets by using different applications. Thus, a packet,application, or group ID is included to identify the different packetstransmitted from the same UE. In this case, a transmitted Tx UE ID, RxUE ID, or group ID may be used to initialize a scrambling sequence of aD2D packet transmitted after an SA, determine a DMRS base sequence, ordetermine a DMRS CS/OCC, etc.

An ID may be information which is important to determine whethercombining is to be performed or not during retransmission. For example,if a UE receiving specific data tries to combine the specific data witha log likelihood ratio (LLR) value (which was received but was notdecoded and has thus been stored in a HARQ buffer) in a state in which aplurality of UEs simultaneously transmit D2D data, data receptionperformance may be degraded when the LLR value is combined with datareceived from another UE. ID information of the UE may be used toinitialize a scrambling sequence of data or to set a DMRS base sequence.

The ID information may include a service ID (or an application ID). If aservice (or application) ID was not obtained at a discovery stage (e.g.,in the case of a D2D signal broadcast without performing discovery), theservice ID may be information which is important to decode data, similarto the UE ID. For example, if one UE transmits data by using a pluralityof applications (e.g., when for a public safety purpose, a photograph istransmitted together with voice), different data items belonging to thesame UE ID should not be combined with each other during retransmission.A UE receiving D2D data may determine whether combining is to beperformed after the service ID and the UE ID are detected.

The above ID information may be directly included in the D2D CI or SAbut may be included in the CI or the SA in the form of a sequenceobtained by performing a Hash function on only the above ID informationor a combination of the above ID information and a different type of IDfor efficient use of resources. For example, the UE ID and the serviceID may be included in the D2D CI in the form of a sequence indicatingIDs, the lengths of which are shortened through an additional Hashfunction, or the ID information may also be used as an input value ofone Hash function to generate a sequence indicating a shortened ID. Asdescribed above, desired information may be more efficiently transmittedby including an ID in a sequence shortened through the Hash functionrather than by directly including the ID in the D2D CI.

An ID indicated by an upper layer may be converted into a physical layerID according to one of hashing, truncation, and a direct usage method,and be then transmitted. In this case, a plurality of IDs among theabove IDs are combined. A portion of an ID to be included in the SA maybe derived from one specific ID, and the other portion thereof may bederived from another specific ID.

A combination of a TX ID and an RX ID may be used in determiningscrambling of a D2D channel, a DMRS sequence, a CS, etc. In particular,the combination of the TX ID and the RX ID may be useful when the numberof bits to be transmitted, for an ID, in a D2DSACH is limited. To thisend, both the Tx UE ID and the Rx UE ID may be included in an ID fieldand transmitted in the D2DSACH. For example, the TX ID and the RX IDwhich are each 8 bits long may be transmitted in the D2DSACH, and 16bits which are a combination of the TX ID and the RX ID may be used toinitialize a scrambling sequence. In the case of D2D broadcasting, theRx UE ID may not be used. In this case, the Rx UE ID may be set to apredetermined specific bit sequence. For example, in the case ofbroadcasting, an 8-bit ID sequence derived from a transmission UE ID maybe transmitted as a Tx UE ID in the D2DSACH, and an Rx UE ID may be setto ‘00000000’ and transmitted. As another example, in the case ofgroup-casting, the Rx UE ID may be set as a group ID.

The whole or a portion of a (physical layer) ID transmitted in the SA(D2DSACH) may be randomly selected by a transmission UE. In particular,only a portion corresponding to a transmission UE ID may be selectivelyand randomly selected and transmitted. Alternatively, the physical layerID may be generated from an upper layer ID. The upper layer ID may beused as a seed value of a random sequence generator. Otherwise, an IDmay be randomly generated regardless of the upper layer ID. The reasonwhy an ID to be included in the SA is randomly set is to minimizecollision between scrambling sequences or DMRSs of UEs when thescrambling sequences are generated or DMRS sequences are selected usingan ID, or to prevent collision between RPTs when the RPTs are determinedusing an ID. Methods of randomly setting an ID to be included in the SAmay include (i) randomly setting an ID in an SA transmission period,(ii) maintaining a randomly determined ID during a predetermined SAperiod and randomly changing the ID after the predetermined SA period,and (iii) continuously transmitting a randomly determined ID, andrandomly selecting an ID only when feedback is received from a specificUE or base station or when a transmission UE recognizes that therandomly determined ID is inappropriate as a result of sensingresources. In one embodiment, an x-bit ID is transmitted in the SA. ThisID may be randomly generated. A target or destination ID may betransmitted in the form of masking CRC of the SA.

The above-described ID information transmitted in the SA may be used forCRC masking which is performed to determine whether D2D data or aD2DSACH is exactly received. In this case, an ID of a D2Dsynchronization signal may also be used. Here, the ID of the D2Dsynchronization signal means the ID of a synchronization signaltransmitted from or relayed by a corresponding node when a specific UEor eNB transmits the D2D synchronization signal. For example, when theexisting cellular synchronization signal reuses the D2D synchronizationsignal, about 500 IDs may be present. In this case, some of CRC maskingbits may be masked by a hashed sequence of an ID indicated (signaled) bya physical layer or an upper layer and the other CRC masking bits may bemasked by a hashed sequence of another specific ID. For example,assuming that there are 24 CRC bits, N predetermined bits may be maskedby a sequence hashed from a UE ID and the other (24-N) bits may bemasked by a sequence hashed from a service or group ID. In anotherembodiment, CRC bits may be double-masked by 24-bit sequences hashedfrom a plurality of IDs (e.g., CRC bit XOR hashed UE ID sequence XORhashed service ID sequence).

A predetermined Hash function may be used for the above ID for CRCmasking but CRC bits may be used as a masking bit sequence by obtaininga ‘truncated bit string’ at a predetermined location from an IDindicated beforehand by a physical layer or an upper layer. In thiscase, an ID truncation location on an ID signaled beforehand by thephysical layer or the upper layer may have been determined. For example,when a Tx UE ID and a target ID are indicated by an upper layer, a bitsequence for CRC masking may be generated from some bits of each of theTx UE ID and the target ID. The length of the bit sequence for CRCmasking may be different from that of an ID included in a controlchannel (which may be a separate D2D control channel or an SA). Thus, amethod of performing truncation/hashing on an ID indicated by an upperlayer for CRC masking and a method of truncating/hashing an upper layerID to generate an ID to be transmitted in a D2D control channel may bedifferent from each other.

When a bit sequence for CRC masking is generated or an ID sequence to betransmitted in the D2D CI is generated, some or all of a transmission ID(source L2 ID), a destination L2 ID, and a synchronization source IDindicated by an upper layer may be used. Such an upper layer ID may bedifferently converted into a physical layer ID according togroup-casting/broadcasting/unicasting. For example, a physical layer IDbit sequence may be generated from only a source ID in the case ofbroadcasting, and may be generated from both of the source ID and agroup (destination) ID in the case of group-casting/unicasting. In thiscase, in the case of broadcasting, the physical layer ID bit sequence isgenerated using only the source ID. Here, all physical layer ID bitsequences may be generated from the source ID, some physical layersequences may be hashed/truncated from the source ID or a group ortransmission ID, and the other physical layer ID sequences may be set topredetermined fixed values (e.g., all zeros or all ones). For example,in the case of group-casting, a physical layer ID sequence may begenerated by using both of a ProSe L2 source ID and a ProSe L2 group IDas a target (destination) ID. In the case of broadcasting, some physicallayer ID sequences may be used as broadcast IDs by designating aspecific bit string of the ProSe L2 group ID and the other physicallayer ID sequences may be set to all zeros. As another example, a bitsequence for CRC masking of a scheduling assignment (SA) may be maskedby some or all of a synchronization source ID, a destination (specificUE or UE group) ID, and a source (Tx) ID. For example, some CRC bits maybe masked by hashing, truncating, or directly using the synchronizationsource ID by using a synchronization source ID and a destination ID, andthe other CRC bits may be masked by hashing, truncating, or directlyusing the destination ID. As another example, CRC bits included in theSA may be masked using the synchronization source ID. If the length ofthe synchronization source ID is shorter than that of the CRC bitsincluded in the SA, the other CRC bits may be padded with Os or befilled by repeating the synchronization source ID, or the other CRC bitsmay be masked by a bit sequence indicating the number of antenna ports(CRC masking bits vary according to the number of APs).

The above-described CRC may be CRC for determining whether controlinformation is exactly transmitted in a separate channel (a physicallayer signal) when the control information is transmitted in theseparate channel, or may be CRC for determining whether a data channel(a physical layer signal of a data transmission region) linked to thecontrol information is exactly transmitted. In this case, the length ofCRC bits for determining whether the D2D CI or SA is exactly receivedand the length of CRC bits for determining whether data is exactlyreceived may be different from each other. For example, the CRC bits forthe SA may be 16 bits long and the CRC bits for the data may be 24 bitslong. In this case, 16 bits should be hashed or truncated from an IDindicated by an upper layer in the SA, and 24 bits should be hashed ortruncated from an ID indicated by the upper layer in the data. In thiscase, a method of generating a bit string for masking the SA and amethod of generating a bit string for masking the data may be differentfrom each other. For example, a bit string for CRC masking may begenerated from both of a source (or Tx) ID and a destination ID (Rx ortarget ID) in the case of the SA (or the data), whereas a bit string forCRC masking may be generated from the source (or Tx) ID, adestination(UE or group) ID, a synchronization source ID, or acombination of two or more IDs among the source (or Tx) ID, thedestination (UE or group) ID, and the synchronization source ID in thecase of ID of the data (or the SA).

d. NDI(New Data Indicator)

When HARQ retransmission is performed between D2D links, an NDI may betransmitted to differentiate between data to be retransmitted and datato be newly transmitted. In this case, the NDI may be transmitted in theform of 1-bit information but may be combined with a UE TX/RX ID ordifferent control information (A/N, CQI, or the like) and transmitted ina new form. For example, the NDI may be used together with the UE TX/RXID and/or an application/service ID as input values of a predeterminedHash function, and an output of the Hash function may be transmitted inthe D2D CI. As another example, an NDI field may be extended to M bits.One of numbers which may be expressed with the M bits may be selectedand transmitted as a specific random number when a UE transmits newdata, and another random number may be selected and transmitted whendata is changed, so that a UE which is receiving D2D data from aplurality of UEs may differentiate data received from a specific UE fromdata received from the other UEs and differentiate this data from datato be retransmitted while the UE decodes the data received from thespecific UE.

e. Information Related to a Plurality of Antennas

Antenna ports (APs) number, the MIMO scheme, precoding information,and/or a precoding granularity may be included in the CI or the SA whenmultilayer transmission or diversity transmission using multipleantennas is allowed in D2D.

The above information may be transmitted in different fields. Otherwise,the above information may be embodied as indicating a specific MIMOscheme or the number of ports for CRC masking a data region. In thiscase, the above information may be set to be always transmitted in asubframe when the number of APs is two or more, and be set to betransmitted in an FSTD when the number of APs is four, so that adiversity scheme may always be used for reliable datatransmission/reception since D2D is more influenced by interference thana cellular environment. When precoding is applied to D2D communication,the precoding information may be included in the D2D CI. In this case,the precoding information and rank information may be includedseparately in the D2D CI, or a PMI and an RI may be expressed togetheras one information item for efficient use of resources (when a codebookincluding a plurality of ranks is included in one precoding set). Whenthe number of APs is two or more, precoding is applied but randomprecoding may be applied. When random precoding is applied, a precodermay be changed in time or frequency units. A granularity to whichprecoding is changed may be determined beforehand. It may be prescribedthat random precoding (precoder/beam cycling) should always be used whenthe number of APs is two or more.

When a transmission UE uses multiple antennas, the number of APs, theprecoding information, and/or the MIMO scheme may be included. Whenmulti-antenna transmission is used, (random) precoding may be used in aD2D data channel. In this case, a precoding granularity oftime/frequency resources in which the same precoding is used may betransmitted in the D2DSACH. When multi-antenna transmission is not used,the precoding granularity may not be included in the D2DSACH or theD2DSACH may be padded with zeros. The number of APs may not beadditionally indicated, and may be indicated such that masking bits varyaccording to the number of ports for CRC.

f. RV (Redundancy Version)

When HARQ retransmission is employed in D2D data communication, an RVmay be included in the CI or the SA. However, when the RV is transmittedin a predetermined order (for example, RV 0->2->3->1) similar to acurrent LTE uplink, the RV may not be included in the CI or the SA evenwhen HARQ retransmission is employed. Otherwise, the RV may be combinedwith specific information of the D2D CI or the SA described above andmapped to an RE, or some fields of the D2D CI may be used to indicatethe RV (e.g., a 2-bit RV). For example, when some states of an MCS fieldare not used in D2D communication, the RV may be transmitted byborrowing a portion of the MCS field. Otherwise, when the RV istransmitted in a separate field, the RV and the NDI may be combined witheach other, expressed as one state on a constellation diagram, andmapped to a control channel.

g. Demodulation Reference Signal (DMRS) Sequence Information

Similar to LTE uplink, when SC-FDMA is employed in D2D communication, aDMRS of a Zadoff-Chu (ZC) sequence base is likely to be used. Tosimplify the DMRS, a ZC-based DMRS such as a cellular system may beused. In this case, a ZC base sequence may be determined based on a cellID but a base sequence having a different ID from the cell ID may beused to be differentiated from the cellular system for an out-coveragecase or an in-coverage case. In this case, a DMRS base sequence betweenD2D UEs may be directly indicated or a predetermined base sequence maybe used. More specifically, some or all of DMRS cyclic shift, a DMRSbase sequence ID, whether a DMRS group/sequence is hopped or not,length, and an OCC may be directly indicated by including the same inthe D2D CI. In this case, a DMRS for decoding the D2D CI may be defineddifferently from a DMRS for data. For example, a predetermined DMRSformat may be used as a format of the DMRS for decoding the D2D CI.Otherwise, the D2D CI may have been coded using differential coding forperforming decoding without the DMRS.

h. Whether Frequency Hopping (Hopping Flag) is to be Used, and NUL_hop

In a frequency domain, a hopping flag and NUL_hop may be transmitted inthe CI or the SA. In this case, when frequency hopping is not used,corresponding bits may not be included or may be padded to a specificstate (e.g., with all zeros). However, when a system bandwidth and/or aband available for D2D communication is relatively low, e.g., when it isless than or equal to a threshold, the above information may not beincluded in the CI or the SA. This is because a frequency hopping gainmay be almost zero when the frequency domain is small.

i. CP Length

If a CP length is not indicated by a D2DSS or a PD2DSCH, the CP lengthmay be indicated in the D2DSACH. In this case, a CP length of theD2DSACH should be determined. One of the following methods may be used.(i) The CP length to be used in the D2DSACH may be signaled beforehandby an upper layer (e.g., an RRC signal) or a physical layer signal (SIBor (E)PDCCH). (ii) A CP length used in a PS S/SSS of a serving cell maybe used as the CP length of the D2DSACH. (iii) A predetermined CP lengthmay be used. The CP length may be fixed beforehand to one of an extendedCP length and a normal CP length. (iv) A CP length may be indicated by asynchronization source, i.e., the D2DSS or the PD2DSCH.

If a plurality of signals are indicated by overlapped each other,priority should be determined. For example, any synchronization sourcemay not be detected by a UE out of coverage in the vicinity thereof atan initial stage. In this case, the extended CP may be basically used.If the synchronization source is detected, a CP length indicated by aD2DSS or a PD2DSCH transmitted from the synchronization source is used.Thereafter, when a signal of an eNB is observed in the vicinity of theUE, a CP length indicated by a PSS/SSS of the eNB is used. Wheninstructions are smoothly received from the eNB, a CP length for theD2DSACH, which is indicated by the eNB, is used. That is, when a CPlength for a predetermined D2DSACH is set and another synchronizationsource or an explicit signal indicating a CP length is received, it maybe prescribed that the CP length should be used.

When the CP length of the D2DSACH is determined as described above, a CPlength of data indicated by the D2DSACH may be indicated by transmittingbits indicating the CP length in the D2DSACH. In this case, the D2DSACHand D2D data may be different from each other in CP length. In thiscase, additional bits may be transmitted in the D2DSACH but an unusedstate of another field may be borrowed and transmitted. Otherwise, theCP length used in the D2DSACH may be directly used. In this case, the CPlength used in the D2DSACH is directly used as a CP length of data. AD2D signal reception UE may detect a CP length by blind-detecting RSintervals of the D2DSACH or a D2D signal or determine the CP length ofthe data by detecting a CP length of a synchronization source or an eNBlinked to the D2DSACH.

An unused bit field of the CI information described above may not befixed to a specific state and may be used for another purpose. Forexample, when frequency hopping is not used, the corresponding bit fieldmay be used to indicate an RPT.

Next, the following may be included, as information which is not relatedto data demodulation, in the CI or the SA.

j. HARQ ACK/NACK

In the case of HARQ ACK/NACK, an ACK/NACK signal may be included in theD2D CI for only a specific service. For example, in the case ofinformation broadcast in an emergency circumstance, D2D datacommunication may be performed without using the ACK/NACK signal so thatthe information may be rapidly spread. However, in the case of a socialnetwork D2D service or the like, data communication may be performedstably by including the ACK/NACK signal in the D2D CI.

k. CQI

When the MCS described above is fixed to a specific service, feedingback of a CQI may be omitted in the service. Alternatively, even if theMCS is fixed, the CQI may be fed back to set transmission (Tx) power. ACQI bit used in this case may be one bit and be included in the D2D CIto determine whether it is greater than a predetermined threshold.

l. PMI, RI [94] When multi-antenna transmission is allowed in D2Dcommunication, a PMI and an RI may also be included in the D2D CI.

m. UE Tx Power

Information regarding UE transmission (Tx) power of a UE transmittingD2D data may also be included in the D2D CI. In this case, a D2Dreception UE may determine an amount of power to be used and an amountof power to be transmitted to the transmission UE when the determinedamount of power is used, based on channel reciprocity. Thus, the UE Txpower may be useful for the D2D reception UE to set Tx power.

n. Transmission Power Control Command (TPC)

When the SINR of a UE receiving D2D data is low, a D2D TPC may also beincluded in the D2D CI. A bit field of the TPC may be expressed with 2bits but may be configured to be greater than 2 bits if needed.

o. Scheduling Request (SR)

An SR between D2D UEs may be used in the form of a warning signalrequesting a predetermined (or randomly selected) specific UE toallocate resources or to first use a specific resource in a situation inwhich an eNB is difficult to access, e.g., an out-of-network coveragesituation or a partial network coverage situation.

Some of the above information that may be included in the D2D CI may betransmitted in a separate D2D control channel format, and the otherinformation may be transmitted by being multiplexed to a D2D datachannel. For example, information such as the RA information may beindicated via a separate control channel and the other information(e.g., the NDI, the MCS, etc.) may be piggybacked on a data channel.

Some of the above information is information related to datademodulation (e.g., the RA information, the MCS, the NDI, the RV, theID, etc.). Some of the above information is information related tofeedback (e.g., the CQI, the PMI, the A/N, etc.) or information which isnot related to data demodulation (e.g., the SR). In this case, theinformation which is related to data demodulation and the informationwhich is not related to data modulation may be transmitted in differentframes. For example, some or all of the information related to datademodulation may be transmitted by being piggybacked on data and theinformation related to feedback may be transmitted in an additionalformat.

RPT Specification

As described above, the CI or the SA may include an RPT which is acombination of time/frequency resources that a transmission UE uses.Hereinafter, the term “RPT” may be understood as resource patterns fordata transmission, and particularly, a T-RPT. If the T-RPT is used, afrequency resource region may have a specific hopping pattern in asubframe indicated by the T-RPT after the subframe is indicated duringfirst transmission. A UE receiving the RPT may receive a D2D signal intime/frequency resources (e.g., a subframe) indicated by the RPT. A bitsequence indicated by an ID field and an RPT field may be a simplebitmap of a subframe for transmission of the D2D signal after the SA istransmitted. For example, 1′s position may be understood as the index ofa subframe via which a UE transmitting the D2D will transmit (willprobably transmit) the D2D signal. In the following description, theterm ‘RPT indication bit sequence’ is used. An RPT bit sequence mayinclude only an ID included in the SA. Otherwise, when an additional bitfield indicating the RTP is included in the SA, the ID and the RPT bitsequence may be understood together as the RPT indication bit sequence.Otherwise, a bit sequence indicating the RPT, which is independent ofthe ID, may be included in the SA. In this case, the RPT bit sequencemay be understood as the RPT indication bit sequence. A set of bitsequences transmitted in the SA and used to indicate the RPT may beunderstood as the RPT indication bit sequence.

If either an SA transmission period or an SA allocation section (thenumber of D2D subframes configured at SA transmission intervals) and thelength of a bit sequence indicating the RPT are different from eachother, a problem may occur. For example, when L D2D subframes arepresent between SA allocation/transmission periods and the number ofbits indicating the RPT is M (here, M≤L), a way of indicating atransmission pattern in the other (L−M) subframes may be a problem. Inthis case, when the length of the RPT indication bit sequence is M, theother L subframes are filled by simply repeating M bit sequences. If Lis not a multiple of M, an RPT may be generated by sequentially fillingthe other L subframes with the other bit sequences. In other words, whenthe number of subframes included in a scheduling assignment period isgreater than the number of bits of the RPT, at least one bit of the RPTmay indicate whether transmission of the D2D signal in two or moresubframes is to be allowed or not. In this case, if the number ofsubframes included in the scheduling assignment period is n times thenumber of bits of the RPT, a UE may repeatedly use the RPT in thescheduling assignment period. If the number of subframes included in thescheduling assignment period is not a multiple of the number of bits ofthe RPT, only a portion of the RPT is used (the bits of the RPT aresequentially used) when the RPT is lastly repeated. The number of bitsof the RPT to be used when the portion of the RPT is used may be equalto a result of dividing the number of subframes included in thescheduling assignment period by the number of bits of the RPT.

As another method, when the length of the RPT indication bit sequence is‘M’, the RPT indication bit sequence represents a bitmap of first Msubframes, and an RPT for the L subframes is generated by filling abitmap of subsequent subframes with the other frames by hopping from thebitmap of the first M subframes to another RPT indication bit sequence.In more detail, when the RPT indication bit sequence has been indexedand an RPT indication bit sequence for the first M subframes isindicated through the SA, an RPT for the other (L−M) D2D subframes isgenerated according to a predetermined index hopping pattern. That is,an additional diversity gain may be obtained or collision may berandomized by hopping between RPTs according to time.

The above methods may be expanded and applied to a method (which will bedescribed below) according to the same principle when an SA transmissionperiod and the number of subframes indicated by the RPT indication bitsequence are different from each other. Even if the RPT indication bitsequence is not a simple bitmap, the above methods may be applied togenerate an RPT for the other (L−M) subframes when a D2D subframe lengthM indicated by the RPT indication bit sequence is less than an intervalL between subframes transmitting the SA (the number of D2D subframesbetween SA transmission periods).

As illustrated in FIG. 8, when the transmission opportunity size for allUEs is M and the number of subframes of a D2D pool is N, a bit sequencemay be M-out-of-N code (Code in which M binary codeword bits among Nbinary codeword bits are set to 1 and the other binary codeword bits areset to 0. Codewords each having a Hamming weight of M are generated fromthe code). An RPT set of M weight may be {β0, β1, . . . , βK−1}. Here,β_(r) denotes an r^(th) RPT sequence that may be expressed with a binarybit sequence having a length N. Here,

$K = {\begin{pmatrix}N \\M\end{pmatrix} = {\frac{N!}{{M!}{\left( {N - M} \right)!}}.}}$In the M-out-of-N code, 1's position represents a data transmissionposition, and 0's position represents a non-data transmission position.When each bit sequence and one of subframe indexes in a D2D resourcepool are mapped in 1:1 correspondence, all 1s' positions are used toindicate subframes in the resource pool. When a group of subframeindexes and ‘1’ of the RPT are mapped in 1:1 correspondence, 1'sposition is used to indicate an index of a subframe group in theresource pool. For example, when a D2D signal is transmitted by bundlingsubframes, the bundled subframes may be understood as ‘1’ of a bitsequence.

In detail, when N=4 and M=2, the following RPT set may be expressed ascodewords of the M-out-of-N code.

RPT set={0011, 0101, 0110, 1001, 1010, 1100}

As another example, when N=5 and M=3, an RPT set is as follows:

RPT set={00111, 01011, 01101, 01110, 10011, 10101, 10110, 11001, 11010,11100}

In some cases, only K1 RPT set indexes among K RPT set indexes may beused. Only the K1 RPT set indexes may be used when all RPT sets cannotbe expressed with the size of an RPT bit field (including an ID field)included in the SA. In this case, a method of selecting K1 RPT setsamong K RPT sets is needed. For convenience of explanation, an originalcodeword set of the M-out-of-N code is referred to as an RPT mother set.It is assumed that a bit sequence of a mother set

$\left\{ {\beta_{0},\beta_{1},\ldots\mspace{14mu},\beta_{{(\begin{matrix}N \\M\end{matrix})} - 1}} \right\}$is indexed according to the following rule.

Here, ‘β_(r)’ denotes an r^(th) RPT sequence.

${r = {\sum\limits_{i = 0}^{M - 1}\left\langle \begin{matrix}{N - s_{i}} \\{M - i}\end{matrix} \right\rangle}},$

where {s_(i)}_(i=0) ^(M−1), (1≤s_(i)≤N, s_(i)<s_(i+1)) contains sortedindexes for 1's positions in β_(r) and

$\left\langle \begin{matrix}x \\y\end{matrix} \right\rangle = \left\{ \begin{matrix}\begin{pmatrix}x \\y\end{pmatrix} & {x \geq y} \\0 & {x < y}\end{matrix} \right.$is an extended binomial coefficient, resulting in a unique label

$r \in {\left\{ {0,\ldots\mspace{14mu},{\begin{pmatrix}N \\M\end{pmatrix} - 1}} \right\}.}$

For convenience of explanation, in this indexing method, bit sequencesof the mother set may be understood as being indexed in ascending orderaccording to the sizes thereof when the bit sequences are converted intodecimal numbers. However, the concept of the present invention may beextended to a case in which the bit sequences are indexed in descendingorder. It is a main point that each bit sequence is indexed to minimizea Hamming distance between two sequences, so that the Hamming distancemay increase when subsets are selected from the mother set at apredetermined interval at a later time and thus an index differencetherebetween increases.

According to another embodiment, an indexing order may be set to asequence selection to be described below. When the indexing order is setto the sequence selection order, K1 RPT subsets may be selectedaccording to the index order.

The following methods may be used to select K1 (≤K) indexes from themother set.

A subset configuration may be signaled by a network or a preconfiguredsubset may be used. K1 set indexes may be transmitted to a D2D UEthrough an upper layer signal or may be preconfigured set indexes.

Subsets may be generated by selecting K1 bit sequences from the motherset in an order in which the K1 bit sequences are indexed.

Otherwise, bit sequences spaced the same distance from one another maybe selected from the mother set in order to maximize a minimum Hammingdistance of an RPT set. However, when a subset size K1 is not a divisorof a mother set size K, a rule of selecting bit sequences spaced thesame distance from one another is difficult to apply. The followingmethod may be used to select indexes spaced the same distance from oneanother if possible.

When the existing mother set indexes 0, 1, . . . , K−1 are divided by‘K’, K representation points 0/K, 1/K, . . . , K−1/K may be obtained.Similarly, when an index of an RPT subset is divided by a set size,0/K1, 1/K1, . . . , (K1−1)/K1 may be obtained. When a representationpoint on a j^(th) RPT subset is located between an i^(th) representationpoint and an (i+1)^(th) representation point on the mother set, i.e.,when (i−1)/K≤(j−1)/K1<i/K, an i^(th) bit sequence of the mother set isused as a j^(th) bit sequence of the RPT subset.

In other words, the above method may be expressed as selecting an index

$\left\lfloor {\frac{K}{K\; 1}i} \right\rfloor,{i \in \left\{ {0,\ldots\mspace{14mu},{{K\; 1} - 1}} \right\}}$from the mother set.

The above method is designed to select subsets spaced the same distancefrom one another if possible when subsets are selected from a motherset. When all UEs randomly select an RPT, a minimum Hamming distancebetween bit sequences selected according to this method is maximized.

In detail, when N=5, M=3, and K1=8, eight sequences should be selectedfrom the mother set (K=10). FIG. 7 illustrates the positions ofrepresentation points of an RPT set between representation points on amother set. Since the distances between the representation points of theRPT set are greater than those of the representation points of themother set (K≥K1), a probability of selecting the same bit sequence fromthe RPT set is zero. Table 1 below shows bit sequences which are finallyselected according to the above method.

TABLE 1 Index Bit sequence 0 00111 1 01011 2 01101 3 01110 4 10101 510110 6 11001 7 11010

The above method may be modified as will be described below.

According to a first method

${\left\lfloor {\frac{K}{K\; 1}i} \right\rfloor + \alpha},{i \in {\left\{ {0,\ldots\mspace{14mu},{{K\; 1} - 1}} \right\}.}}$That is, a predetermined offset α may be applied when subsets areselected from a mother set. Bit sequences spaced the same distance fromone another are selected form the mother set by applying thepredetermined offset α. The offset may be in a range of 0 tofloor(K/K1)−1. The offset may be a predetermined value. Alternatively,the offset may be a value configured by an eNB or another UE. Forexample, the eNB may instruct a specific UE or a specific UE group touse a specific offset. Otherwise, the offset may be set in connectionwith a synchronization source ID such that different RPTs are employedbetween synchronization groups. Otherwise, the offset may be set inconnection with the synchronization source ID and/or a hop count suchthat different RPTs are used between different hops. For example, whenK=20 and K1=4, 0, 1, 2, 3, or 4 may be considered as the offset. An RPTsubset is {0, 5, 10, 15} when the offset is ‘0’, and is {1, 6, 11, 16}when the offset is 1.

According to a second method,

${\left\lceil {\frac{K}{K\; 1}i} \right\rceil + \alpha},{i \in \left\{ {0,\ldots\mspace{14mu},{{K\; 1} - 1}} \right\}},$which is a modified version of a function selected from a mother set,may be used. That is, a ceiling function is used rather than a floorfunction. Similarly, the above-described offset α may be further appliedin the second method.

A specific RPT may be determined based on an ID included in the SA andan RPT bit field. In this case, when the ID has a property of beinghardly changed and the RPT bit field has a property of being relativelyeasily set by a transmission UE, RPT sets may be grouped based on eachbit field.

One of three methods illustrated in FIG. 8 may be used for grouping ofthe RPT sets.

Referring to FIG. 9(a), when the length of an ID included in an SA is‘N’ and an RPT set size is ‘K1’,

$\frac{K\; 1}{2^{N}}$RPTs may be sequentially grouped. In this case, RPT indication bitsincluded in the SA may be used to indicate a group to which an RPT of aspecific UE belongs. In this case, an ID field is used to indicate anRPT to be used in the group, so that different RPTs may be indicatedwith the RPT indication bits if possible. If a UE does not appropriatelytransmit data due to collision, different resources may be selected ifpossible by differently set RPT bits.

As illustrated in FIG. 9(b), when the length of an ID included in an SAis ‘N’, the ID may be used to indicate an RPT group and a bit sequenceof an RPT field may be used to indicate a specific RPT in the RPT group.

FIG. 9(c) illustrates a case in which when the length of an ID includedin an SA is ‘N’, the ID is used to indicate an RPT group and a bitsequence of an RPT field is used to indicate a specific RPT in the RPTgroup. In this case, in order to select RPTs which are distant from eachother with only RPT bits if possible, RPTs which are distant from eachother may be classified as one group during grouping of RPT sets. In oneembodiment, when an N-bit ID is transmitted in an SA and L RPT bits aretransmitted, an RPT set size is 2^(L+N). In this case, one group isformed by collecting RPTs spaced a distance of 2^(N) from each other,and is indicated using the ID transmitted in the SA. Thereafter, aspecific RPT is indicated using RPT bits included in the SA.

A subframe indicated by an RPT indication bit sequence may be a generalsubframe without classifying the subframe as a D2D subframe or a non-D2Dsubframe. In this case, when a D2D subframe is indicated by a differentsignal, an index of a subframe through which a D2D signal is to beactually transmitted may be indicated by performing a logic ANDoperation on D2D subframe indication bits and the RPT indication bitsequence.

The above-described RPT may be indicated according to a method whichwill be described below.

In mode I in which a UE directly receives an instruction regarding aresource region from a base station, an eNB may indicate an ID and RPTbits, which are to be transmitted in an SA, in a D2D SA grant. In thiscase, an ID sequence transmitted in the SA and/or a sequence of an RPTbit field transmitted in the SA (a bit field indicating specific IDand/or RPT) may be explicitly included in the D2D grant. Otherwise, abit sequence of a D2D-RNTI may be hashed, or an ID sequence and/or anRPT bit field which is to be transmitted in the SA may be generatedusing some bits (e.g., lower N bits). Here, the “D2D-RNTI” means an IDsignaled beforehand to differentiate D2D control information fromdifferent control information. The RNTI is used to mask CRC bits of theD2D control information. In this case, a portion of the ID to betransmitted in the SA may be generated from the RNTI and the other IDmay be generated based on a target ID (or a group ID). Here, the ID tobe transmitted in the SA may change with time. In this case,characteristically, only a Tx UE ID portion is variable since when atarget UE ID portion is hopped to and this fact is not known to targetUEs, detection cannot be exactly performed. If a hopping pattern of thetarget UE ID portion is known to a target UE, all ID sequences includedin the SA may be hopped according to a predetermined rule. Thechangeability (hopping) of the ID sequence according to time may beachieved by differently setting a bit field in the D2D grant by an eNBor the ID sequence may change according to a specific rule after the D2Dgrant is received from the eNB. For example, the ID sequence included inthe D2D grant may be used as an initialization parameter of a randomsequence and a sequence which changes with time may be generated from arandom sequence generated using this parameter.

In mode 2 in which a UE receives a signal regarding a resource pool andresources for D2D communication are selected, an ID may be transmittedvia the SA and used to determine an RPT. Here, the ID may be understoodas an ID having a short length and derived from an ID (transmissionand/or reception (target, group) ID) at an upper layer or as a bitsequence to be used to set either a position to which data is to betransmitted or a scrambling parameter. If a large number of RPTcandidates cannot be generated due to the short length of the IDincluded in the SA, collision between IDs is highly likely to occur. Inthis case, the same RPT may be used by a large number of Tx UEs. Toprevent this problem, bits indicating a specific RPT may be transmittedin some bits of the SA. Otherwise, the specific RPT may be indicatedusing a combination of bits of an ID bit field and bits of an RPT fieldin the SA. For example, the ID included in the SA may be used toindicate an RPT set and an RPT indication bit included in the SA may beused to indicate a specific index in the RPT set. As another example,RPT bits included in the SA may be used to indicate a specific RPT setin a resource pool, and the ID included in the SA may be used toindicate the specific RPT in the pool/set indicated by the RPT bits. Inthis case, bits indicating the RPT set may be semi-staticallytransmitted rather than being transmitted in each SA. For example, thebits indicating the RPT set may be transmitted in every n^(th) SA, ormay be used for a virtual CRC purpose on the assumption that this bitdoes not change until the SA is transmitted n times even when the bitsindicating the RPT set are transmitted in each SA. The RPT bits may betransmitted by borrowing MCS bits or an unused state of another SA bitfield rather than being additionally included. Otherwise, both ofadditionally included bits and an unused state of another bit field maybe used to indicate the RPT.

The size of the RPT bits to be used to indicate the SA may varyaccording to the size of a D2D UE group or the number of Tx UEsbelonging to the group. For example, when N policemen belong to aspecific police group, the size of bits to be used to indicate the RPTmay be set to log 2 (N). In this case, the other unused bits may be usedfor another purpose or may be set to 0 to be used for a virtual CRCpurpose.

In modes 1 and 2, an ID of an RPT may be set according to differentmethods. For example, only a Tx UE ID may be used to indicate an RPT inmode 1, whereas both the Tx UE ID and a target UD ID (group ID) may beused to indicate an RPT in mode 2.

The following information may be further used to set the RPT.

i) Information regarding a transmission opportunity size in view of oneUE: This information is information indicating the number of resourcesto be allocated to the UE from one SA.

ii) Information regarding a number of times of retransmitting eachtransmission block (TB): This information may be expressed differentlyas information indicating the number of TBs to be transmitted withrespect to one transmission opportunity. In this case, the number oftimes of retransmitting each TB may be calculated by transmissionopportunity size/the number of TBs to be transmitted in one SA.Otherwise, this information may be expressed as information indicating a(maximum) number of times of repeating each TB.

Some of the above information may be preconfigured or may be configuredby a network. In the case of a UE out of coverage, the information maybe preconfigured or may be signaled with a physical layer signal or anupper layer signal from another UE in the network. Some of theinformation may be transmitted in an SA. For example, the transmissionopportunity size may be preconfigured or may be configured by a network.In this case, the number of times of retransmitting each TB may betransmitted in the SA. On the contrary, the information regarding thetransmission opportunity size may be transmitted in the SA, and thenumber of times of retransmitting each TB may be preconfigured or be avalue indicated semi-statically with an upper layer signal by thenetwork.

Specifically, assuming that an 8-bit ID is transmitted in the SA, thenumber of RPTs that may be identified with IDs is 2^8=256. Assuming thatthe number of subframes of a resource pool in mode 2 is 16 and thetransmission opportunity size is 8, the number of RPTs that may begenerated is ₁₀C₈=12870. Thus, the RPTs cannot be identified only withID bits included in the SA and thus additional bits indicating the RPTmay be transmitted in the SA according to the above-described method. Inthe present embodiment, about 6 bits are additionally needed to identifyall the RPTs that may be generated. All the RPTs may be indicated usingeither a combination of unused MCS states and a new bit field or anadditional bit field.

Channel Structure for CI

The above-described CI may be transmitted via a PUCCH type channel, aPUCCH piggyback type channel, a channel having a new channel structure(e.g., a D2DSACH), etc. Cases in which the above-described CI istransmitted using these channels will now be described in detail. Thatis, the structure of a physical D2D Control Channel (PD2DCCH) will bedescribed below. If the PD2DCCH includes resource allocationinformation, the PD2DCCH may be referred to as a D2DSACH or an SA.

The PD2DCCH may be configured as a PUCCH type. Basically, the PUCCH typeis likely to be transmitted in a subframe or slot separately from D2Ddata. A location to which the D2D CI is to be transmitted may be set asa region to which a D2D control signal is to be transmitted according tothe number of RBs configured beforehand as D2D control channeltransmission regions at a specific location (e.g., an edge portion) inthe frequency domain, similar to a PUCCH region. In this case, when a UEtransmitting a D2D signal is a UE permitted to simultaneously transmit aPUSCH/PUCCH, the D2D CI and D2D data may be transmitted together in thesame slot or subframe. When a PUCCH type D2D control channel is used,information included in a control channel may be some or all of the D2DCI described above. This structure is transmitted separately from a D2Ddata channel and thus the RA information indicating resource allocationinformation of the D2D data channel may be included therein. The MCS,the NDI, etc. may also be included in the structure. Alternatively, onlythe RA information may be transmitted to a region separately from dataand the other CI such as the MCS, the NDI, etc. may be multiplexed intoa data region. A format in which the above information is transmitted islikely to be PUCCH format 2 or PUCCH format 3. This is because formats 2and 3 are designed to transmit more bits than format 1. However,transmission of D2D CI in a format such as PUCCH format 1 is notexcluded in the present invention. This is because the size of the D2DCI transmitted separately from D2D data may be small or a large numberof resources of the PUCCH format 1 may be occupied by one UE.

One UE may encode the D2D CI (which may include the RA information, theMCS, the NDI, etc.) to be transmitted and then transmit the same in theabove format. A PUCCH index to be used in this case may be linked to aCCE index of a control channel indicated by a D2D scheduling node (aneNB or a specific UE) or one of N candidate positions (which areconfigured, for example, as RRCs) indicated beforehand by the schedulingnode may be selected and transmitted. In this case, the selecting of oneof the candidate positions indicated beforehand by the scheduling nodemay be performed by directly receiving an instruction from thescheduling node (for example, one of the candidate positions may beincluded in DCI or a position of using a PUCCH resource may be indicatedby borrowing a TPC field or another field) or by determining a candidateposition by selecting one of the candidate positions by a UE. In thiscase, one UE may use a large number of PUCCH indexes to transmit a D2Dcontrol channel unlike the existing PUCCH index. For example, one UE maytransmit the D2D control channel by occupying M PUCCH indexes. FIG.10(a) illustrates a case in which two PUCCH indexes are used to transmitone D2D CI item. In this case, D2D CI of one UE may be mapped to the MPUCCH indexes in a predetermined order. The reason why one UE uses alarge number of PUCCH indexes is because the size of the D2D CI mayexceed the number of bits that may be included in one PUCCH index.

Multiplexing of a D2D data region and a D2DCCH having a PUCCH format:Resources of a PUCCH and a PUSCH should be consecutively allocated toeven a UE, which is not permitted to simultaneously transmit the PUCCHand the PUSCH, so as to transmit a PUCCH type control channel. Thus, alocation having the PUCCH format and at which a D2D control channel isto be transmitted may be a predetermined specific PRB pair in a PUSCHregion of D2D data. For example, a first (or last) PRB pair of an RBtransmitting D2D data may transmit a PUCCH type D2D control channel.Alternatively, for each D2D subframe, the first PRB pair and the lastPRB pair may be alternately used as the position of a D2DCCH (so as toobtain an effect of frequency-hopping the D2DCCH).

FIG. 10(b) illustrates a case in which for each D2D sub-channel, a firstPRB pair is set as a D2D CI transmission channel. When PUCCH format 3 isused, one PRB pair may transmit coded 48 bits and be multiplexed intoD2D data and thus one UE may use the whole OCC. Thus, in this case, D2DCI corresponding to a multiple of the length of the OCC to be used maybe transmitted (e.g., 5*48 coded bits may be transmitted when the OCClength=5). In this method, in order to maintain a single carrierproperty, the D2D CI is transmitted using a PRB pair which has the PUCCHformat but is consecutive to a D2D data region. Similarly, informationincluded in the D2D control channel may be some or all of theinformation listed above.

The PD2DCCH may be configured as a PUSCH piggyback type. When anexisting UCI is piggybacked on a PUSCH, the D2DCI may be transmitted bypuncturing or rate-matching some REs of a data region. In this case, theREs may be sequentially used for D2D CI mapping in a clockwisedirection, starting from a virtual low subcarrier index included in anRB, similar to a manner of transmitting a CQI/PMI during piggybacking ofthe existing UCI. In this case, in D2D communication, some of symbols atan edge of a subframe are not likely to be used due to Tx/Rx switchingas illustrated in FIG. 11(a). Thus, when the D2D CI is piggybacked on aD2D subframe and is ‘time-first’ mapped starting from a low subcarrierframe similar to a CQI/PMI, the following operation is suggested.

A first symbol and/or a last symbol may be excluded in D2D CI mapping.This is because the first symbol and/or the last symbol are likely to beused as a guard period due to Tx/Rx switching. For AGC training, somesamples consecutive to the guard period are not likely to be used toreceive data. Thus, in this case, the D2D CI may not be mapped to asymbol including the guard period. In some cases, one or more symbolsare likely to be used for the guard period and AGC training and thus asymbol to which the D2D CI is mapped may be configured beforehandaccording to the guard period and an AGC training period. For example, asymbol to which the D2D CI may be mapped may be included in a D2Dsynchronization channel, configured as an RRC, or determined beforehand.As described above, the D2D CI is mapped to a symbol that may be fullyused but D2D data may be mapped to a symbol which is partiallypunctured. Otherwise, the D2D data may be mapped only to an SC-FDM (orOFDM) symbol that may be fully used, similar to the D2D CI, and only areference signal may be mapped to a symbol which is partially punctureddue to Tx/Rx switching. It may be prescribed that the reference signalbe mapped to the first symbol and/or the last symbol only when the D2DCI is piggybacked on a D2D data region, so that when the D2D CI istransmitted together with the D2D data, the precision of channelestimation may be increased to improve a capability of decoding data andcontrol information.

Alternatively, the D2D CI may be mapped only to an even-numbered (or oddnumbered) subcarrier of the first symbol and/or the last symbol. Due tothis structure, a first symbol and/or a last symbol of a D2D subframemay be mapped through 30 kHz subcarrier spacing, similar to an SRS.Thus, even if some symbols cannot be used for Tx/Rx switching or AGC dueto repeated transmission of the same symbol in the time domain, thesymbols may be restored. FIG. 11(b) illustrates that D2D CI or D2D datais not mapped to odd-numbered REs of first and last symbols.

In an existing UCI piggybacking scheme, an A/N or an RI is mapped to asymbol near a DMRS. According to this method, information having highimportance among D2D CI information is arranged near the DMRS to achievehigh channel estimation performance. In this case, when a guard periodis used in a first or last symbol of a D2D subframe, a location on asymbol to which D2D CI is to be mapped should be adjusted. Inparticular, in the case of an extended CP, since an RI may be mapped toa first symbol, the D2D CI may be punctured and thus a serious loss mayoccur in receiving data when the D2D CI is mapped.

First, in the existing UCI piggybacking scheme, a column set used for anRI and a HARQ-ACK is as shown in Tables 2 or 3 below.

TABLE 2 CP configuration Column set Normal {1, 4, 7, 10} Extended {0, 3,5, 8}

TABLE 3 CP configuration Column set Normal {2, 3, 8, 9} Extended {1, 2,6, 7}

Piggybacking of a HARQ-ACK and an RI on a normal CP is illustrated inFIG. 12(a). An extended CP is illustrated in FIG. 12(b). In this case,when a first symbol or a last symbol is used as a guard period, the RIcannot be mapped. Typically, this situation occurs in some D2D subframesand thus a solution therefor is needed.

If D2D CI is mapped to the vicinity of a DMRS, first, some CI havinghigh importance among the D2D CI may be mapped to the vicinity of theDMRS. In this case, as in the existing PUSCH piggybacking scheme, theD2D CI is sequentially filled with specific information throughfrequency-first mapping in a predetermined symbol order, starting fromthe vicinity of the DMRS (mapping may be performed starting from a highvirtual carrier index in this case but may be performed starting from alow virtual carrier index), rather than mapping the specific informationto another symbol according to importance. For example, the D2D CI, suchas an MCS, an ID (which is shortened through hashing), etc., issequentially filled in the vicinity of the DMRS and is then sequentiallyfilled in symbols in a predetermined order after one symbol.

Alternatively, after the number of required symbols is determinedaccording to the whole bit size of the D2D CI mapped to the vicinity ofthe DMRS, REs of a corresponding symbol may be ‘frequency-first’punctured (puncturing may be performed starting from an RE having a highvirtual subcarrier index or an RE having a low virtual subcarrier indexin this case) (otherwise, data is rate-matched in consideration of REsto be used for CI) and then coded bits of the D2D CI are ‘time-first’mapped to a corresponding region.

Alternatively, the D2D CI mapped to the vicinity of the DMRS is‘time-first’ punctured according to an SC-FDM symbol determinedbeforehand according to the whole bit size, and coded bits of the D2D CIare ‘time-first’ mapped to a corresponding region.

Specifically, in the case of a normal CP, an order of symbols to befilled with the D2D CI may be 3->8->2->9->4->6->1->10. In the case of anextended CP, an order of symbols to be filled with the D2D CI may be2->6->1->7->3->5->8.

In both the normal CP and the extended CP, a first symbol and/or a lastsymbol is not used for D2D CI mapping. When a guard period is used foronly the first symbol or the last symbol, the D2D CI is not mapped to asymbol including the guard period.

The D2D CI is sequentially filled, starting from the vicinity of theDMRS. The D2D CI may be filled in a symbol between two DMRSs in thevicinity of the DMRS earlier than external symbols. This is becausehigher channel estimation performance may be achieved through channelinterpolation between the DMRSs.

Next, as in the existing PUSCH piggybacking scheme, symbols to which theD2D CI is mapped is determined beforehand according to the importancethereof, but symbols which are likely to include a guard period or whichinclude the guard period are excluded in D2D CI mapping. In this case,among the D2D CI, information having high importance will be referred toas ‘D2D CI class A’ and information having relatively low importancewill be referred to as ‘D2D CI class B’. These terms are merely used torepresent the importance of the information and thus the presentinvention should not be limited by these terms. For example, the D2D CIclass A may include a UE ID, an MCS, etc., and the D2D CI class B mayinclude information regarding the number of APs, a MIMO technique, etc.The above classes according to the D2D CI may be determined beforehand.

Examples of the above suggestion are shown in Tables 4 and 5 below.

TABLE 4 CP configuration Column set Normal {2, 3, 8, 9} Extended {1, 2,6, 7}

TABLE 5 CP configuration Column set Normal {1, 4, 7, 10} Extended {3, 5,8, 9} or {3, 4, 5, 8}

In a D2D subframe, the D2D CI is not mapped to a symbol which is used asthe guard period or which is likely to be used as the guard period.

The D2D CI may be mapped to a predetermined symbol position according tothe importance thereof (see Tables 4 and 5). Furthermore, additionalchannel coding may be used according to the importance of the D2D CI.For example, information having high importance may be first mapped to asymbol in the vicinity of a DMRS through RM coding or low-rate coding. Asymbol having low importance may be mapped to a symbol at a positionrelatively distant (from the DMRS) simply through repetitive coding orsimplex coding. Alternatively, the contents of the D2D CI may be encodedthrough one channel coding technique (e.g., convolutional code)regardless of the importance thereof, and mapped to a control channelseparately from an RE or data according to one of the above methods.

Device configuration according to embodiment of the present invention

FIG. 13 is a diagram for configuration of a transmit point apparatus anda user equipment according to embodiment of the present invention.

Referring to FIG. 13, a transmit point apparatus 10 may include areceive module 11, a transmit module 12, a processor 13, a memory 14,and a plurality of antennas 15. The antennas 15 represent the transmitpoint apparatus that supports MIMO transmission and reception. Thereceive module 11 may receive various signals, data and information froma UE on an uplink. The transmit module 12 may transmit various signals,data and information to a UE on a downlink. The processor 13 may controloverall operation of the transmit point apparatus 10.

The processor 13 of the transmit point apparatus 10 according to oneembodiment of the present invention may perform processes necessary forthe embodiments described above.

Additionally, the processor 13 of the transmit point apparatus 10 mayfunction to operationally process information received by the transmitpoint apparatus 10 or information to be transmitted from the transmitpoint apparatus 10, and the memory 14, which may be replaced with anelement such as a buffer (not shown), may store the processedinformation for a predetermined time.

Referring to FIG. 13, a UE 20 may include a receive module 21, atransmit module 22, a processor 23, a memory 24, and a plurality ofantennas 25. The antennas 25 represent the UE that supports MIMOtransmission and reception. The receive module 21 may receive varioussignals, data and information from an eNB on a downlink. The transmitmodule 22 may transmit various signals, data and information to an eNBon an uplink. The processor 23 may control overall operation of the UE20.

The processor 23 of the UE 20 according to one embodiment of the presentinvention may perform processes necessary for the embodiments describedabove.

Additionally, the processor 23 of the UE 20 may function tooperationally process information received by the UE 20 or informationto be transmitted from the UE 20, and the memory 24, which may bereplaced with an element such as a buffer (not shown), may store theprocessed information for a predetermined time.

The configurations of the transmit point apparatus and the UE asdescribed above may be implemented such that the above-describedembodiments can be independently applied or two or more thereof can besimultaneously applied, and description of redundant parts is omittedfor clarity.

Description of the transmit point apparatus 10 in FIG. 13 may be equallyapplied to a relay as a downlink transmitter or an uplink receiver, anddescription of the UE 20 may be equally applied to a relay as a downlinkreceiver or an uplink transmitter.

The embodiments of the present invention may be implemented throughvarious means, for example, hardware, firmware, software, or acombination thereof.

When implemented as hardware, a method according to embodiments of thepresent invention may be embodied as one or more application specificintegrated circuits (ASICs), one or more digital signal processors(DSPs), one or more digital signal processing devices (DSPDs), one ormore programmable logic devices (PLDs), one or more field programmablegate arrays (FPGAs), a processor, a controller, a microcontroller, amicroprocessor, etc.

When implemented as firmware or software, a method according toembodiments of the present invention may be embodied as a module, aprocedure, or a function that performs the functions or operationsdescribed above. Software code may be stored in a memory unit andexecuted by a processor. The memory unit is located at the interior orexterior of the processor and may transmit and receive data to and fromthe processor via various known means.

Preferred embodiments of the present invention have been described indetail above to allow those skilled in the art to implement and practicethe present invention. Although the preferred embodiments of the presentinvention have been described above, those skilled in the art willappreciate that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention. For example, those skilled in the art may use a combinationof elements set forth in the above-described embodiments. Thus, thepresent invention is not intended to be limited to the embodimentsdescribed herein, but is intended to accord with the widest scopecorresponding to the principles and novel features disclosed herein.

The present invention may be carried out in other specific ways thanthose set forth herein without departing from the spirit and essentialcharacteristics of the present invention. Therefore, the aboveembodiments should be construed in all aspects as illustrative and notrestrictive. The scope of the invention should be determined by theappended claims and their legal equivalents, and all changes comingwithin the meaning and equivalency range of the appended claims areintended to be embraced therein. The present invention is not intendedto be limited to the embodiments described herein, but is intended toaccord with the widest scope consistent with the principles and novelfeatures disclosed herein. In addition, claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by subsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

Embodiments of the present invention are applicable to various mobilecommunication systems.

What is claimed is:
 1. A method of transmitting a device-to-device (D2D)signal by a UE in a wireless communication system, the methodcomprising: selecting resources for transmission of a schedulingassignment from a resource pool for the scheduling assignment; andtransmitting the scheduling assignment through the resources, whereinthe scheduling assignment comprises information including a firstresource pattern for transmission (RPT) corresponding to a first bitmapfor a scheduling assignment, wherein each bit of bits of the first RPTindicates whether the D2D signal is transmitted in at least one subframeof subframes included in a period for scheduling assignment, and whereinat least one subframe not indicated by the first RPT is indicated by asecond RPT hopping the first RPT in a predetermined hopping pattern whenthe subframes included in the period for scheduling assignment aregreater in number than the bits of the first RPT.
 2. The methodaccording to claim 1, wherein the scheduling assignment furthercomprises a modulation and coding scheme (MCS) to be used in thescheduling assignment period.
 3. The method of claim 2, wherein the MCSindicates only some of modulation techniques to be used when the UEtransmits/receives a signal to/from the base station.
 4. The method ofclaim 3, wherein the some modulation techniques do not comprise 64quadrature amplitude modulation (QAM).
 5. The method of claim 1, whereinthe scheduling assignment further comprises a plurality of RPTs groupedinto a plurality of RPT groups, an ID field related to the UE using thescheduling assignment and an RPT indication field, wherein the ID fieldindicates a specific RPT group among the plurality of RPT groups, andwherein the RPT indication field indicates a specific RPT in thespecific RPT group.